Real-time Refocusing of Spaceborne SAR Images for Ship Targets with Space-variant Motion Based on GPU

Traditional spaceborne synthetic aperture radar (SAR) imaging algorithms are primarily designed for stationary targets. However, in practical scenarios, ship targets are often affected by complex angular motions induced by sea winds and waves, resulting in significant blurring in SAR images. This angular motion is inherently nonlinear and space-variant. This paper proposes a refocusing method tailored for ship targets with complex space-variant motion. The method decomposes the ship target image into multiple subimages and estimates phase errors of each subimage by maximizing image contrast, thereby achieving fine refocusing. Additionally, an acceleration scheme for refocusing processing is designed based on spaceborne hardware platforms, aimed at onboard real-time processing. The effectiveness of both the refocusing method and the acceleration scheme is validated using real spaceborne SAR image data. Experiment results demonstrate that, compared to traditional refocusing methods, the proposed approach improves the imaging quality of ship targets with complex motion. The refocusing processing efficiency is greatly enhanced, meeting the real-time processing requirements.